--- description: Rails Service Objects Guide applyTo: "app/services/**/*.rb" --- # Rails Service Objects Guide ## Core Philosophy - Service objects encapsulate complex business operations - Keep services focused on single responsibilities - Make services easy to test and understand - Use services to keep models and controllers thin - Design for reusability and composability ## When to Use Service Objects - Complex operations spanning multiple models - External API integrations - Multi-step processes with transactions - Business logic that doesn't fit naturally in models - Operations requiring detailed error handling - Background job processing logic ## Service Design Principles - One service, one responsibility - Clear, descriptive naming that explains the operation - Consistent interface across services - Explicit dependencies and parameters - Predictable return values and error handling ## Naming Conventions - Use verb-based names that describe the action - Include the domain context in the name - Examples: `UserRegistrationService`, `PaymentProcessor`, `OrderFulfillment` - Keep names specific and intention-revealing - Avoid generic names like `UserService` ## Service Structure - Include ActiveModel modules for validations when needed - Define clear public interface - Keep implementation details private - Use dependency injection for testability - Document complex logic thoroughly ## Input Handling - Validate inputs early and clearly - Use ActiveModel::Attributes for parameter handling - Define explicit attribute types - Provide meaningful validation messages - Handle optional parameters gracefully ## Return Values - Return consistent, predictable results - Use success/failure pattern for operations - Include relevant data in responses - Provide clear error information - Consider using Result objects for complex returns ## Error Handling - Anticipate and handle expected failures - Use exceptions for unexpected errors - Provide actionable error messages - Log errors with appropriate context - Design for graceful degradation ## Transaction Management - Wrap related database changes in transactions - Handle rollbacks appropriately - Keep transactions as short as possible - Document transaction boundaries - Test rollback scenarios ## Testing Service Objects - Test services in isolation - Mock external dependencies - Verify success and failure paths - Test edge cases thoroughly - Ensure idempotency where appropriate ## Dependency Injection - Inject dependencies through initialization - Avoid hard-coded dependencies - Use interfaces for external services - Keep services loosely coupled - Document required dependencies ## Service Composition - Build complex operations from simple services - Keep services composable and reusable - Avoid service objects calling other services directly - Use orchestrator services for complex workflows - Maintain clear boundaries between services ## Background Job Integration - Design services to work synchronously and asynchronously - Keep job classes thin, delegate to services - Handle job failures gracefully - Make services idempotent for retries - Log job execution appropriately ## External API Integration - Isolate API logic in dedicated services - Handle API failures gracefully - Implement appropriate retry logic - Cache API responses when sensible - Monitor API usage and errors ## Performance Considerations - Profile service execution time - Optimize database queries - Consider caching expensive operations - Batch operations when possible - Monitor resource usage ## Service Organization - Group related services in modules - Keep service files in app/services - Organize by domain or feature - Maintain consistent file structure - Document service relationships ## Common Patterns - Form objects for complex input handling - Query objects for complex database queries - Presenter objects for view logic - Policy objects for authorization rules - Workflow objects for multi-step processes ## Anti-Patterns to Avoid - God services that do too much - Services that mirror controller actions - Anemic services with no real logic - Services tightly coupled to specific views - Services that bypass model validations ## Refactoring to Services - Extract complex model methods - Move controller logic to services - Consolidate scattered business logic - Simplify fat models - Improve testability ## Documentation Standards - Document service purpose clearly - Explain complex business rules - Provide usage examples - Note performance considerations - Include error handling details ## Integration Guidelines - Call services from controllers - Use services in background jobs - Compose services for complex operations - Keep services framework-agnostic when possible - Design for future API exposure ## Best Practices Summary - Keep services focused and single-purpose - Make dependencies explicit - Handle errors gracefully - Write comprehensive tests - Design for reusability Remember: Service objects are about organizing complex business logic. Keep them focused, testable, and easy to understand.